The present invention relates to a grommet, and more specifically, to a waterproof grommet assembly for a connector.
A conventional waterproof grommet is typically molded from a soft synthetic resin, such as rubber. Synthetic resins have elasticity and have a high degree of adhesion. The characteristics of the resin afford the grommet waterproofing properties and enable the grommet to be compressed so that it can be readily attached to a connector.
The use of a soft synthetic resin, however, is associated with a plurality of drawbacks. For example, when the grommet is compressed for attachment to a connector housing, the through-holes formed in the waterproof grommet are crushed and deformed by the compression causing the through-holes to shift. Further, in the case of a connector that has a plurality of contacts, if the plurality of contacts is inserted into the waterproof grommet in order from one side, a bias pressure is generated in the vicinity of the through-holes containing electrical wires. The pressure causes the through-holes into which electrical wires have not yet been inserted to shift. Because in either case the through-holes no longer correspond with the contact cavities, gaps are created between the waterproof grommet and the inner surface of the connector housing when contacts are inserted, causing the sealing properties of the waterproof grommet to deteriorate.
One method of addressing these drawbacks is shown in Japanese Utility Model Registration No. 2503949 (FIG. 4). This Utility Model discloses a grommet with protruding parts 143 disposed inside a connector housing 140 that engage in recessed parts 123 of the waterproof grommet 111. The assembly prevents the positions of the contact cavities 141 or through-holes 121 from shifting either when a compressive pressure is applied to the grommet or when a plurality of contacts are inserted from one side. Because a soft synthetic resin is used, however, when contacts connected to electrical wires are inserted into the through-holes of the grommet, splitting occurs on the inner surfaces of the through-holes. As a result, water is capable of entering the grommet through the split areas.
It is therefore desirable to develop a waterproof grommet, which reduces the splitting effects of the inner surfaces of the through-holes formed in the waterproof grommet without causing any deterioration of the waterproof properties.
This invention relates to a waterproof grommet having a first sealing member and a second sealing member. The first member has a first sealing part formed on the inner surface of a through-hole through which an electrical wire connected to a contact is passed. The first sealing part adheres tightly to the electrical wire. The second member has a second sealing part formed on the outer surface of the through-holes that adheres tightly to the connector housing. The first member is formed from an elastic material that has a lower hardness than that of the second member. As a result, splitting of the inner surface of the through-holes is prevented without causing any deterioration of the waterproof properties of the joint between the connector housing and the waterproof grommet.